Screening-machine.



J. W. BELL.

SCREENING MACHINE. APPLICATION FILED JULY 3:,1'911.

Patented Jan. 14, 1919.

lmren/ar Jab W- Ber/l JOHN W. BELL, 0F MONTREAL, QUEBEC, CANADA.

scnnnme-lncmm.

Specification of Letters Patent.

Patented J an. 14, 1919.

7 Application filed July 81, 1917. Serial No. 188,744.

To all whom it may concern:

Be it known that I, JOHN W. BELL, a subject of the King of Great Britain, and resident of the city of, Montreal, in the Province of Quebec and Dominion of Canada. have invented certain new and useful Improvements in Screenin -Machines, of which the following is a fufi, clear, and exact description.

- This invention relates to improvements in screening apparatus, and is particularly designed for classifying finely divided mate rials such as sand in commercial or laboratory tests, and the object of the invention is to provide a screening or classifying apparatus which will be simple and durable in The screens are arranged to be continuously revolved during the operation, which I'GVO;=-:- lution combined with the incllnatlon oft-he apparatus produces a constant and satisfactory distribution of the material on the screens.

In the drawings which illustrate the invention:

Figure 1 is a front elevation of the device;

Fig. 2 is a view partly in section on the vertical axis of themachine.

Referring more particularly to the drawings. 11 designates a base which may be of any suitable structure, and 12 a framework pivoted in the base on trunnions 13, so that it. may be set at any desired inclination and locked by means of clamping bolts 14 passing tlirough slots 15 in the base. The frame 12 comprises uprights 16 connected at the top by transverse members 17 and 18, at an intermediate point by transverse members 19, and near the bottom by atrans-.

verse member 20. The members 17 and 18 carry bearings 21 inwhich the vibrating I mechanism operates. The members 19 form the members 19. The lower transverse member 20 carries a tubular bearing or cylinder 1n which the supporting post of the screen slides.

The screening device proper consists of a bottom pan 26, and a series of superposed screen trays 27 of any suitable and well known construction. The pan is supported on a table'28 having a post or spindle 29 which is slidable through the'members 19,- worm wheel 22 and bearing 25. This post is also revoluble in the members 19 and bearing 25, but is irrevoluble with respect to the worm wheel by reason of a key-way- 30 formedin the post, in which the worm wheel engages. A spring 31 is mounted in the bearing 25 between an adjustable head 32 at the bottom of the bearing and the lower end of the post 29, so that the spring constantly urges the post upward.

At the upper end of the frame, a shaft 33 is provided between the members 17 and 18 and bearing in the upright frame members 16. This shaft carries a cam 34 which is completely inclosed in a casing 35 mounted in the vibrating spindle 36. vThe casing contains a small roller 37 with which the cam engages to cause movement of the vibrator in one direction. Movement of the casing relative to the shaft is permitted by slots 38 in the casing through which the shaft passes. The lower portion of the vibrator rod 36 is provided with an adjustable stop 39 and lock nut 40, and the extremity 41 bears on the center of the cover 42 of the screening device.

The cam shaft 33 and worm shaft 23 are geared together by any suitable means such as the pulleys 43 and belt 44. A spring catch 45 may be provided on one of the uprights 16 to hold the table 28 in depressed posit-ion.

' Theoperation of the device is extremely simple. The nest of screens is manually de-' pressed until the supporting table 28 passes the catch 45 which holds the table in de-' pressed position. During this downward movement the post 29 supporting the table slides downwardly, compressing the spring replaced and the catch withdrawn so that the spring 31 raises the screens until upward movement is stopped by the cover engaging the tip of the vibrating rod 36. Rotation is now imparted to one of the shafts of the machine, for example, the worm shaft 23, which by means of the worm wheel 22 slowly rotates the screens. The cam shaft 33 is driven from the .worm shaft, and therefore the cam makes a considerable number of revolutions for each revolution of the screens especially if the gearing is such as to drive the cam shaft faster than the worm shaft. On each revolution of the cam, it engages the roller 37 and thereby depresses the vibrating rod 36 against the action of the spring 31. As soon as the throw of'the cam passes the roller, the spring exerts itself to thrust the screens violentlyu ward as far as the stop 39 will permit. he'material on the screens of course travels up with the screens and on the sudden stoppage of screen movement the particles of material on the screens tend to continue movement, and are thus thrown off the screensand then fall back. In this way, the material is kept constantly agitated and works very rapidly through the screens. The rotation of the screens combined with this rotation keeps the material spread in-a layer of approximately uniform thickness over the full surface of each screen, so that material sifts through very rapidly. The inclination of the screening device and the return of upward movement of the screens may be regulated according to the class of material to be treated.

After the operation has been .continued for sufficient time, the apparatus is stopped and the screening device opened in the same manner as described in connection with filling same. The various screens are separated and the amount of material on each noted. The compression of the spring 31 may be regulated'in accordance with the amount of travel or irrespective thereof, so that comparatively gentle vibration may be combined with considerable screen movement, or a very violent agitation with very little screen movement. In this way, the screen may be adjusted to have the maximum efficiency .With any class of material.

It has been found that apparatus constructed according to the preceding description is peculiarly efiicient both from the accuracy of the results produced and the very short time occupied as compared with existing screening machines. The rapidity of action is a valuable feature, but accuracy of results is still more important, and it is in this latter feature that the device is particularly notable. An understanding of the term accuracy will be best arrived at from a consideration of the following example A sample of sand is placed in the apparatus, and the machine operated for say three minutes (accurate timing). The machine is now opened, and the sand remaining on each ofthe screens and in the pan weighed accurately. If the sand from all screens and the pan is now mixed together and the screening operation repeated for the same length of time, the weights of sand on the various screens will be found practically. identical, .with the results of the first operation. In the same way, the screening operation may be repeated any number of times and the results will be nearly identical. Obviously, if the same sample of sand is used repeatedly, the grains will gradually reduce in size by wear and fracture so that slightly more finegrained sand will be found after the final operation than after the first, but this is a feature which need not enter into consideration for pratcical purposes. A result such as above outlined is alto ether different from that obtained with ordlnary screening machines or hand screening. With ordinary machines or hand screening, the same sample, if treated a dozen or twenty times, .will in all probability give as many different results. Where very accurate classifying is essential, it has been necessary to make a number of tests and average the result. With this machine, the results may be re lied upon as accurate. Furthermore, the time consumed is much less for each operation than when other apparatus is used. In actual test, apparatus constructed according to this invention will effect a thorough classification in about one-sixth of the time required by an ordinary screening machine.

I attribute the high efiiciency of this apparatus to the inclination and slow rotation of the screens combined with rapid vibration. For instance, with an inclination of 3 to 4, a speed of three to five revolutions per minute and four hundred to four hundred and fifty blows per minute, the results produced are satisfactory, but it will be understood that the invention is in no way limited to these details. Another feature, which is of considerable importance both in the rapidity and accuracy of the screening, is the method of vibration' by checking upward movement of the screens so that material is thrown up from the screens. By this action, the blinding or choking of the screens by particles'wedged in'the mesh is reduced to a minimum. A judicious combination of screen inclination and rotative speed causes the material to be at all times uniformly distributed over the surface of the screens. The percussive action of the apparatus naturally tends to work material which will not pass through the screens to the lowest points thereof. Proper timing of the revolution with relation to the inclination and nature of thematerial will resame rate that it works down, so that a layer of uniform thickness is maintained over the screens, which obviously facilitates the screening both b utilizing the entire area and by facilitating separation of the particles as they jump from the screens' For screening certain materials such as pulp samples containing a large amount of fine fioury material of lightweight, the reverse action of the apparatus may be employed with advantage, that is to say, the vibrating mechanism may bearranged to lift the screens, and the spring to drive them violently downward. This result may be produced with the present apparatus by placing the screens in the apparatus in inverted position and then inverting the whole apparatus, or where the machine is specially designed for such work, by transposing the rotating and vibrating features shown.. If it is not desired to use the full number .of screens shown in the drawings, 0 en-bottom fillers may be used to replace trays,'or the upper transverse members 17 and 18 may be made adjustable. The speed ratio between the shafts 23 and33 may be varied as desired by using different sizes of ulleys or gears 43.

aving thus described my invention, what I claim is 1. In a device of the class described, a plurality of superposed screens, a screen vibrating mechanism including a cam mechanism to move the screens in one direction and a spring to move the screens in the opposite direction, said screens being mounted in compression between the cam mechanism and spring and means for rotating the screens simultaneously with the vibration thereof.

2. In a device of the class described, a revoluble and reciprocatable spring pressed screen support, screens thereon, an a reciprocating member holding the screens on said support. j Y

3. Ina device according to the preceding claim, adjustable means for limiting the spring induced movement of the screens and support.

he screen.

port, means for operating said member tointermittently move the screens and sugport a ainst the action of the spring, an a justab e stop for limiting spring impelled movement 0 he screens and support, and a latch positioned to hold the support in posi-- tion to free the screens from their holding member.

6. In a device of the class described, a frame, a series of superposed screens therein, a screensupporting table, a 0st carrying said table slidably and revolu ly mounted in the frame, a guide for said post, a spring therein engaging the end of the post,

an adjustable seat for-said spring, a worm gear slidably but irrevolubly connected with the post, and a worm journaled in the frame meshing with said worm wheel.

7. In a device according to the preceding claim, a reciprocating member including a housing arranged to move the screens in the opposite direction to the'spring, a shaft, a cam thereon within saidhousing, a roller within the housing engageable by the cam, a fixed stop, and an adjustable stop on the reciprocating member engageable with the fixed stop.

8. In a device'according to the preceding claim, a base in which the framework is adjustably mounted, and driving connectlon between the worm shaft and cam shaft.

9. In a device-according to claim 7 a latch on the frame positioned to engage and hold the screen table at its point of maximum depression.

In witness whereof, have hereunto set.

my hand. 1

JOHN W. BELL. 

